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Analysis of a sample from the asteroid Bennu has revealed essential life components and hints of a watery past, offering insights into the origins of the solar system and prebiotic chemistry.

• Early analysis of the Bennu asteroid sample returned by NASA‘c OSIRIS-REX the mission revealed dust rich in carbon, nitrogen and organic compounds, all of which are essential components for life as we know it. Dominated by clay minerals, particularly serpentine, the sample reflects the type of rock found at Earth’s mid-ocean ridges.
• The magnesium-sodium phosphate found in the sample suggests that the asteroid may have broken off from an ancient, small, primitive ocean world. The phosphate was a surprise to the team, as the mineral was not detected by the OSIRIS-REx spacecraft while it was at Bennu.
• While a similar phosphate was found in the Ryugu asteroid sample delivered by JAXA(Japan Aerospace Exploration Agency’s) Hayabusa2 mission in 2020. The magnesium sodium phosphate found in the Bennu sample is notable for its purity (i.e. the absence of other materials incorporated into the mineral) and its grain size, unprecedented in any meteorite sample.

This Bennu mosaic was created using observations made by NASA’s OSIRIS-REx spacecraft, which was in close proximity to the asteroid for more than two years. Credit: NASA/Goddard/University of Arizona

Discoveries of the composition of asteroid Bennu

Scientists eagerly awaited the opportunity to dig into the pristine 4.3-ounce (121.6-gram) asteroid Bennu sample collected by NASA’s OSIRIS-REx (Origin, Spectral Interpretation, Resource Identification and Security – Regolith Explorer) mission. since it was delivered to Earth last fall. They hoped the material held secrets from the solar system’s past and the prebiotic chemistry that may have led to the origin of life on Earth. An early analysis of the Bennu sample recently published in Meteoritics and Planetary Sciencesshows that this excitement is justified.

The OSIRIS-REx sample analysis team found that Bennu contains the original ingredients that formed our solar system. Asteroid dust is rich in carbon and nitrogen, as well as organic compounds, all of which are essential components for life as we know it. The sample also contained magnesium sodium phosphate, which was a surprise to the research team as it was not seen in the remote sensing data collected by the Bennu spacecraft. Its presence in the sample suggests that the asteroid may have broken off from a long-extinct, small, primitive ocean world.

View of eight sample trays containing the final material from asteroid Bennu. The dust and rocks were poured into the trays from the top plate of the Touch-and-Go Sampling Mechanism (TAGSAM) head. 51.2 grams were collected from this outpouring, bringing the final mass of the asteroid sample to 121.6 grams. Credit: NASA/Erika Blumenfeld and Joseph Ebersold

Analysis of the Bennu sample has revealed intriguing insights into the asteroid’s composition. Dominated by clay minerals, particularly serpentine, the sample reflects the type of rock found at Earth’s mid-ocean ridges, where material from the mantle, the layer beneath the Earth’s crust, meets water.

This interaction not only results in the formation of clay; it also results in various minerals such as carbonates, iron oxides, and iron sulfides. But the most unexpected discovery was the presence of water-soluble phosphates. These compounds are components of the biochemistry for all known life on Earth today.

While a similar phosphate was found in the Ryugu asteroid sample delivered by JAXA’s (Japan Aerospace Exploration Agency) Hayabusa2 mission in 2020, the magnesium-sodium phosphate found in the Bennu sample stands out for its purity—that is, the absence of other materials in the mineral—and its grain size, unprecedented in any meteorite sample.

A small portion of the Bennu asteroid sample returned by NASA’s OSIRIS-REx mission, shown in microscope images. The upper left window shows a dark Bennu particle about a millimeter long, with an outer shell of bright phosphate. The remaining three panels show progressively magnified views of a fragment of the particle that has detached along a bright vein containing phosphate, imaged by a scanning electron microscope. Credit: From Lauretta & Connolly et al. (2024) Meteoritics and Planetary Sciencesdoi:10.1111/maps.14227

The finding of magnesium-sodium phosphates in the Bennu sample raises questions about the geochemical processes that concentrated these elements and provides valuable clues about the historical conditions of Bennu.

“The presence and state of phosphates, along with other elements and compounds on Bennu, suggest a watery past for the asteroid,” said Dante Lauretta, co-author of the paper and principal investigator for OSIRIS-REx at the University of Arizona, Tucson. “Bennu could potentially have once been part of a wetter world. However, this hypothesis requires further investigation.

“OSIRIS-REx gave us exactly what we hoped for: a large pristine sample of an asteroid rich in nitrogen and carbon from a once-wet world,” said Jason Dworkin, co-author of the paper and OSIRIS-REx project scientist at NASA’s Goddard Space Flight Center in Greenbelt, Maryland.

NASA’s OSIRIS-REx spacecraft leaves the surface of asteroid Bennu after taking a sample. Credit: NASA Goddard Space Flight Center/CI Lab/SVS

Despite its possible history of interaction with water, Bennu remains a chemically primitive asteroid, with rudimentary proportions closely resembling those of the Sun.

“The sample we brought back is the largest reservoir of unaltered asteroid material on Earth right now,” Lauretta said.

This composition offers a glimpse into the early days of our solar system, more than 4.5 billion years ago. These rocks have preserved their original state, having neither melted nor solidified since the beginning, which confirms their ancient origin.

The team confirmed that the asteroid is rich in carbon and nitrogen. These elements are critical to understanding the environment in which Bennu’s materials originated and the chemical processes that transform simple elements into complex molecules, potentially laying the foundations for life on Earth.

“These findings highlight the importance of collecting and studying material from asteroids like Bennu — especially low-density material that normally burns up upon entering Earth’s atmosphere,” Lauretta said. “This material holds the key to unraveling the complex processes of solar system formation and the chemistry of prebiotics that could have contributed to the emergence of life on Earth.”

Dozens more laboratories in the United States and around the world will receive pieces of the Bennu sample from NASA’s Johnson Space Center in Houston in the coming months, and many more scientific papers describing analyzes of the Bennu sample are expected in the next few years by the Sample Analysis Team OSIRIS-REx.

“The Bennu samples are hauntingly beautiful alien rocks,” said Harold Connelly, co-author of the paper and OSIRIS-REx sample scientist at Rowan University in Glassboro, New Jersey. “Each week, analysis by the OSIRIS-REx sample analysis team provides new and sometimes surprising discoveries that help place important constraints on the origin and evolution of Earth-like planets.”

Launched on September 8, 2016, the OSIRIS-REx spacecraft traveled to the near-Earth asteroid Bennu and collected a sample of rocks and dust from the surface. OSIRIS-REx, the first US mission to collect a sample from an asteroid, delivered the sample to Earth on September 24, 2023.

Reference: “Asteroid (101955) Bennu in the laboratory: Properties of the sample collected by OSIRIS-REx” by Dante S. Lauretta, Harold S. Connelly, Joseph E. Abersold, Connell M. O’D. Alexander, Ronald-L. Ballouz, Jessica J. Barnes, Helena C. Bates, Carina A. Bennett, Laurinne Blanche, Erika H. Blumenfeld, Simon J. Clemett, George D. Cody, Daniella N. DellaGiustina, Jason P. Dworkin, Scott A. Eckley, Dionysis I. Foustoukos, Ian A. Franchi, Daniel P. Glavin, Richard C. Greenwood, Pierre Haenecour, Victoria E. Hamilton, Dolores H. Hill, Takahiro Hiroi, Kana Ishimaru, Fred Jourdan, Hannah H. Kaplan, Lindsay P. Keller, Ashley J. King, Pierce Koefoed, Melissa K. Kontogiannis, Loan Le, Robert J. McCoy, Timothy J. McCoy, Ralph E. Milliken, Jens Nyorka, Anne N. Nguyen, Maurizio Paiola, Anjani T. Pollitt, Kevin Reiter, Heather L. Roper, Sarah S. Russell, Andrew J. Ryan, Scott A. Sandford, Paul F. Scofield, Cody D. Schultz, Laura B. Seifert, Shogo Tachibana, Kathy L. Thomas-Keprta, Michelle S. Thompson, Valerie Tu, Filippo Tusberti, Kun Wang, Thomas J. Zega , CWV Wolner and , 26 June 2024 Meteoritics and Planetary Sciences.
DOI: 10.1111/maps.14227

NASA’s Goddard Space Flight Center in Greenbelt, Maryland, provided overall mission management, systems engineering, and safety and mission assurance for OSIRIS-REx. Dante Lauretta of the University of Arizona, Tucson, is the principal investigator. The university leads the science team and the mission’s science monitoring and data processing planning. Lockheed Martin Space in Littleton, Colorado, built the spacecraft and provided the flights. Goddard and KinetX Aerospace were responsible for the navigation of the OSIRIS-REx spacecraft. Preparation for OSIRIS-REx is taking place at NASA Johnson. International partnerships on this mission include the OSIRIS-REx laser altimeter from CSA (the Canadian Space Agency) and the asteroid sampling science collaboration with JAXA’s Hayabusa2 mission. OSIRIS-REx is the third mission in NASA’s New Frontiers Program, managed by NASA’s Marshall Space Flight Center in Huntsville, Alabama, for the agency’s Science Mission Directorate in Washington.